The present invention relates to air cargo transportation, and more particularly to devices for tensioning and locking air cargo net straps.
The device of the present invention can most advantageously be used as part of the equipment in the baggage and cargo holds of aircraft.
A known device for tensioning and locking air cargo net straps, fitted to the cargo nets in the cargo holds of aircraft incorporates a case composed of parallel webs interconnected by two shafts and rigidly attached by means of a square thrust shank. In addition, the device comprises a spring-loaded two-arm lever arranged on a shaft between the webs near the thrust shank. One arm of the lever, facing the thrust shank, extends radially and is provided with small teeth. The center of the lever arm's radial edge is offset in relation to the hinge axis of the lever.
The fixed end of the cargo net strap is attached to the shaft at the shank end located farther from the thrust shank, and the free end of the strap is passed above the other shaft and around the thrust shank. The strap brought above the thrust shank contacts the teeth of the lever and turns the latter about the axis thereof. Inasmuch as the teeth are located on an eccentric circumference, they sink in the strap body when the lever is turned, and lock the strap inside the device.
In order to unlock the device and to release the free strap end, the free end of the lever must be pushed. Hence, the lever turns and disengages the teeth from the strap which can easily be pulled out of the device. The spring of the lever moves it back to the initial position.
Disadvantages inherent in the known device include excessive wear of the straps due to the action of the lever teeth, and inadequate safety in locking the device.
Another known device for tensioning and locking cargo mooring straps comprises a U-shaped case whereto a lever embracing the case is pivoted by means of a shaft. Like the case, the lever is U-shaped. The fixed strap end is fastened to the bottom case section by means of a shaft. The lugs on the side surfaces of the top case section mount another shaft, whereas the side walls are provided with radially extending projections formed by a part of the circumference with the centre thereof aligned with that of a hole accommodating the lever shaft. There are recesses located between the shaft-mounting lugs and the radially extending projections. Oval slots in the sides of the lever carry a movable shaft, and the top lever end receives a cross piece.
For threading the strap into the device, the cross piece is moved down and turned. Hence, the lever shaft slides over the radial lugs of the case.
The free strap end introduced into the device embraces the lever hinge shaft and the other lever shaft, and runs outside above the cross piece of the lever. The strap placed to a stretched position is tensioned fully after the lever is transferred from the bottom to the top position, whereat the lever shaft enters the recesses between the radial lugs and the shaft-mounting lugs, thereby clamping the lever in the uppermost locked position. Then the free strap end is passed through the slot between the outer surface of the lever and the shaft mounted in the side lugs of the case for secure locking of the lever in the closed position.
To unlock the device, the free strap end is pulled upward, then the cross piece of the lever is pushed and turned downward. The lever placed to the lower-most position permits pulling the free strap end out of the case of the device.
Disadvantages inherent in this device are as follows:
(a) with a load applied to the straps, considerable force is required for unlocking the device; PA1 (b) inadvertent unlocking of the device is possible because mutual location of the shaft and lever shaft does not provide for safe locking of the closed device components if the strap end is not fitted into the device which is quite possible in service; PA1 (c) locking of the device by the strap end is not quite suitable for use because the lever seizes the strap end, and thereby impedes unlocking of the device during opening.